Central bank governor Godwin Emefiele said foreign reserves in January stood at around $28 billion compared with $37 billion in June 2014.

Nigerian commercial banks told customers on Sunday they would allow deposits of foreign currency to be transferred abroad from their accounts, just days after the central bank announced it was easing restrictions on foreign cash deposits.

Africa's biggest economy and top oil producer has been hit hard by the drop in crude prices since it relies on oil sales for about 95 percent of its foreign reserves.

The central bank last week announced that it would allow commercial banks to accept cash deposits of foreign currency, reversing a restriction imposed last year when such deposits were banned to curb speculation.

Its policy shift came days after International Monetary Fund head Christine Lagarde told Nigerian lawmakers that the IMF did not support foreign exchange restrictions.

Stanbic IBTC and Guaranty Trust Bank (GT Bank) were among two commercial banks which sent emails and text messages to customers informing them that transfers of foreign cash to accounts in other countries, which had also been prohibited, were now acceptable.

"You can now transfer foreign currency cash deposits made into your GT Bank domiciliary account(s) via internet banking, Mobile App or at any of our branches nationwide, subject to a daily cumulative limit of $10,000," GT Bank said in an email.